Respirators were first developed in response to the use of chemical warfare agents in the First World War. Nearly all respirators have several common features-a seal suitable for forming a seal against the face, thus providing a cavity into which air is inhaled via a filter that removes noxious materials from the inhaled air. The seal prevents ingress of ambient, potentially foul, air into the cavity and thus into the lungs of the wearer. Air is drawn into the cavity either by the negative pressure caused by inhalation of the wearer or by the use of a positive pressure exerted, for example, by a pump. The respirators also normally comprise some sort of eyepiece.
U.S. Pat. No. 4,574,799 and GB 1587812 describe a respirator comprising both an oronasal mask and an outer face-sealing mask, wherein, in use, the oronasal mask forms a seal around the oronasal region of the face of the wearer and defines a cavity between itself and the outer mask such that substantially no pressure difference forms between the ambient atmosphere and the cavity between the oronasal mask and the outer mask that would allow ingress of ambient air into the cavity formed between the seal of outer mask and face and allows for compensation in the drop in pressure during inhalation that may lead to ingress of unwanted material via disrupted seal.
WO 02/11816 discloses a dual cavity respirator similar to those described in U.S. Pat. No. 4,574,799 and GB 1587812. The respirator of WO 02/11816 also comprises an ocular mask in gaseous communication with the oronasal mask. The ocular mask protects the eyes against potential damage should foul air enter the cavity between the outer mask and the oronasal mask. However, several problems have been experienced with such a respirator. It is difficult to incorporate the seals of the ocular and oronasal masks into the relatively small area defined by the size of the face of the wearer and so construction of the respirator is relatively complex and expensive. Furthermore, it is difficult to develop a seal on the ocular mask that fits all users due to the large variation of head and face shapes.
The respirator of the present invention seeks to overcome some or all of these problems.